Plant, Property and Equipment, Net - Schedule of Plant, Property and Equipment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Plant, Property and Equipment, Net
Total plant, property and equipment	$ 2,611.8		$ 2,611.8		$ 2,462.8
Less accumulated depreciation	(1,569.8)		(1,569.8)		(1,467.7)
Plant, Property and Equipment, Net	1,042.0		1,042.0		995.1
Depreciation expense	48.4	$ 48.1	148.6	$ 142.2
Gains (losses) on write offs or sales of head end and customer premise equipment	0.0	$ 0.1	0.3	$ 0.4
Distribution facilities
Plant, Property and Equipment, Net
Total plant, property and equipment	1,447.5		1,447.5		1,336.4
Customer premise equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	376.1		376.1		376.9
Head-end equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	316.3		316.3		299.9
Telephony infrastructure
Plant, Property and Equipment, Net
Total plant, property and equipment	127.7		127.7		123.8
Computer equipment and software
Plant, Property and Equipment, Net
Total plant, property and equipment	101.3		101.3		95.4
Vehicles
Plant, Property and Equipment, Net
Total plant, property and equipment	34.9		34.9		32.1
Buildings and leasehold improvements
Plant, Property and Equipment, Net
Total plant, property and equipment	43.9		43.9		44.9
Office and technical equipment
Plant, Property and Equipment, Net
Total plant, property and equipment	32.5		32.5		36.2
Land
Plant, Property and Equipment, Net
Total plant, property and equipment	6.2		6.2		6.7
Construction in progress (including material inventory and other)
Plant, Property and Equipment, Net
Total plant, property and equipment	$ 125.4		$ 125.4		$ 110.5